Structurally integrated composite members



June 30, 1964 H. M. HADLEY 3,138,899

STRUCTURALLY INTEGRATED COMPOSITE MEMBERS Filed Oct. 15, 1959 "gamma? 8 INVENTOR. HOME/2 M. HADLEY rawm A TTORNE Y6 United States Patent 015 ice 3,138,899 Patented June 30, 1964 3,138,899 STRUCTURALLY INTEGRATED COMPOSITE MEMBERS Homer M. Hadley, King County, Wash. (911 Securities Bldg., Seattle 1, Wash.) Filed Oct. 15, 1959, Ser. No. 846,577 2 Claims. (Cl. 50395) This invention concerns the structural integration of one or more metal elements, such as a plate or the flange of a beam, with one or more concrete elements which contact a surface of the metal element, such for example as a roadway slab, or the metal element may be a vertical column or pilaster contacting a concrete wall.

Various types of shear connectors, so-called, have been utilized heretofore to effect structural bonding between, for example, a metal bridge stringer and a concrete roadway slab poured over the top flange of such a stringer. These shear connectors take various forms, such as small channels, angles, Zs, etc., welded to the top of the metal beams, upstanding therefrom and completely embedded within the concrete when poured. After the concrete has attained its strength these shear connectors usually perform two functions--they act in shear to prevent horizontal slippage of the concrete relative to the beam, and they act in tension to prevent lifting upward of the concrete slab, that is, separation of the concrete from the metal, as it may tend to do under the action of heavy vehicle loads when the slab is continuous over a number of stringers. Another form of shear connector now extensively used is a mechanically welded headed stud, Which resembles the headed end of a blank bolt in appearance.

Because such shear connectors have the dual function of resisting shear and resisting tension, there must be enough of them, closely enough spaced, and of such formation, as to discharge this dual function, whereas if these two functions were assigned one to one type of connector and the other to a different type thereof, each could be greatly simplified and the aggregate number of connectors could be lessened. According to present practice, using connectors having the dual function, since the tensional connectors must be reasonably deeply embedded within the concrete, rather considerable areas of metal are opposed to the longitudinal movement in shear or slippage of the concrete slab with respect to the surface of the metal beam whereon the slab rests, and each must be strong enough to resist such slippage by bending or by their resistance to bending, about a center of resistance located some distance, for example several inches, above the surface of the beam where slippage would occur. This involves large moment arms, hence quite large and strong sections, and very strong welding attachment to the beam. Conversely, since shear resistance occurs at or close to the surface of the beam, but is distributed over the entire area of that surface, there must be many more such connectors than mere resistance to tensional loading would require. Thus the use of dual-function connectors increases the number and complicates the structure thereof.

The present invention has as its object the virtual elimination of dual-function shear connectors, and the substitution of multiple centers of resistance, to shear only, substantially at the plane of the contacting surfaces of the metal and the concrete elements, and of tensional connec tors separate from these shear resistors. Tensional loads, resisting separation of the two elements, and by so doing insuring integrity of the shear bond otherwise effected between them, is assumed by these other connectors, few in number, and collecting inadequate to resist shear loading.

In addition, this invention materially lessens the cost of attaining such structural integration, leaves the metal surfaces freer from obstructions and hence safer for workmen to Walk thereon, and can be employed whether the concrete element is poured in place or precast.

The drawings illustrate the invention as employed in several representative forms.

FIGURE 1 illustrates in a broken-away isometric View a poured slab bonded to a metal beam.

FIGURE 2 is a similar view, illustrating the employment of a precast slab.

FIGURE 3 is a transverse section through the slab of FIGURE 2 and the upper part of the beam, illustrating the completed bond.

FIGURE 4 is a broken-away isometric view of a steel plate bonded, according to the principles of this invention, to concrete slabs poured against its opposite surfaces.

In essence the present invention comprises preliminarily roughening the surface of the metal element, as by chipping or scoring with a jack-hammer, or with an areair gouger which melts spots on the surface and then blows away the molten metal from shallow spot craters or indented troughs, and leaves some upraised metal. Preferably the metal surface is roughened by applying weld metal, in upstanding points or ridges. All such operations, and others, give the normally smooth rolled surface numerous surface irregularities distributed over the portion which is to contact the concrete. In addition, tension-resisting members are anchored to and project from the roughened surface of the metal element, each preferably having heads or equivalent portions at their outer ends. The number of these tension-resisting members is much less than the number of the usual shear connectors, and they can usually be rather widely distributed. Their various forms will be described hereinafter.

The concrete element is next brought into contact with the roughened surface. It may be poured in place, embedding the surface irregularities and the tension-resisting elements. On the other hand, it may be precast, and if so its surface adjacent the roughened surface of the metal element is roughened, as by the application of known inhibitors to inhibit setting of the cement in such areas to leave the aggregates exposed. Also, if precast, apertures of a type described hereinafter will be formed for the reception of each tension-resisting member, and these apertures also are a form of surface-roughening. Such a precast concrete element is disposed with its roughened surface closely adjacent but slightly spaced from the roughened metal surface, and a rich mortar is poured between them, and into the apertures of the precast slab to embed the tension-resisting members. This mortar when set becomes in effect an integral part of the concrete element. Upon the mortar setting, or in the first case upon the poured concrete attaining its strength, an immediate bond is present to resist shear, in the form of the interengagement of the concrete, or mortar, with the roughness of the surface irregularities of the metal element, and in the case of the precast slab, with the ir regularities of its roughened surface. This would not suflice to maintain them in contact during use except that the tension-resisting members strongly resist separation of the tWo, and it is this that insures the adequacy of the shear bond between them. Thus multiple individual shear resistors and means to resist separation cooperate to assure, in superior manner, what formerly was attempted by the known types of shear connectors alone.

In FIGURE 1 the bearing surface or flange of a metal beam 1 has multiple weld points 3 upstanding from it at closely spaced intervals, and a few headed blank bolts 4 applied at infrequent intervals and upstanding to a height less than the thickness of the concrete slab 2 which ultimately is poured upon such flange. The set concrete embeds all the weld points 3, and the blank bolts 4. The

latter resist separation of slab 2 from beam 1, and so long as separation can not occur the resistance of the weld points 3 to shear loads is more than adequate.

The shear resistors need not be points, if raised, and might be depressions, as has been indicated above. FIG- URE 2 shows Weld ridges 30 at frequent intervals. This figure also shows the slab 2a as precast, and apertured at intervals at 5 to receive the upstanding ends of threaded rods 9 which receive washers l2 and nuts 11. The rodreceiving apertures 5 are preferably conical or flared towards the exit distant from the beam 1. Spacer pads 6 space the adjacent, irregular surfaces of slab 2a and beam 1, and marginal felt strips 7 act in a sense as forms,

to contain a rich mortar filling 8 between these irregular surfaces, and within the apertures 5, embedding the rods 9 and locking the slab to the beam, when fully set, for the part-conical inverted filling of the aperture 4 can not pull out through the small end of the aperture. The threaded rods 9 can be threaded into nuts 10 welded to the beams surface, after the slab has been positioned properly. Thereby there is no upstanding projection of appreciable height during handling and placement of the slab.

FIGURE 4 illustrates how a steel plate 13 is bonded and structurally integrated between two concrete slabs 14. Weld points, ridges, or as shown, the sinuous ridge 3b are applied to both surfaces of the plate, and then tie bars 15 are passed through holes 16 punched in the plate. The ends of the tie bars may be angled or otherwise headed. Upon pouring, the concrete at 14 embeds the plate and its shear resistors 3b, and its separation resistors 15.

I claim as my invention:

1. A composite structural member comprising in combination a load-sustaining metal element and a precast concrete element applied to a surface of the metal element, a plurality of surface irregularities distributed over the adjacent surface of the metal element, and the adjacent surface, of the concrete element being also rough, a mortar filling interposed between such surfaces and bonding together the metal and the concrete elements through said irregularities and roughness, to resist shear loads, nuts anchored to the irregular surface of the metal element, the concrete element having apertures which when the concrete element is in place are positioned to register with said nuts, and headed rods outstanding in the several apertures and threadedly received in the corresponding nuts, said rods being inadequate to resist the shear loads, the mortar filling embedding said rods and nuts and filling the several apertures, whereby the rods act in tension to hold the concrete element against separation from the metal element, and the roughened surfaces so held together resist shear loads.

2. A composite structural member as in claim 1, wherein the outer end of each rod is threaded, and the head thereof is threaded upon such threads.

References Cited in the file of this patent UNITED STATES PATENTS Re. 18,492 Friedrich June 14, 1932 855,204 Scofield May 28, 1907 1,245,395 Smulski Nov. 6, 1917 1,303,741 Thomas May 13, 1919 1,355,572 Ross Oct. 12, 1920 1,415,304 Bray May 9, 1922 1,475,846 Marks Nov. 27, 1923 1,885,883 Young Nov. 1, 1932 2,028,169 Sahlberg Jan. 21, 1936 2,151,399 White Mar. 21, 1939 2,269,490 Slick Jan. 13, 1942 2,319,049 Fischer May 11, 1943 2,331,140 Schmidt Oct. 5, 1943 2,341,777 Hensel Feb. 15, 1944 2,466,106 Hoge Apr. 5, 1949 2,479,476 Cueni Aug. 16, 1949 2,602,321 Blair July 8, 1952 FOREIGN PATENTS 586 Great Britain 1894 44,983 Austria Nov. 10, 1910 935,557 France Feb. 2, 1948 943,001 France Sept. 27, 1948 901,842 Germany Jan. 14, 1954 784,383 Great Britain Oct. 9, 1957 OTHER REFERENCES Civil Engineering, pp. 46-48, August 1948. 

1. A COMPOSITE STRUCTURAL MEMBER COMPRISING IN COMBINATION A LOAD-SUSTAINING METAL ELEMENT AND A PRECAST CONCRETE ELEMENT APPLIED TO A SURFACE OF THE METAL ELEMENT, A PLURALITY OF SURFACE IRREGULARITIES DISTRIBUTED OVER THE ADJACENT SURFACE OF THE METAL ELEMENT, AND THE ADJACENT SURFACE OF THE CONCRETE ELEMENT BEING ALSO ROUGH, A MORTAR FILLING INTERPOSED BETWEEN SUCH SURFACES AND BONDING TOGETHER THE METAL AND THE CONCRETE ELEMENTS THROUGH SAID IRREGULARITIES AND ROUGHNESS, TO RESIST SHEAR LOADS, NUTS ANCHORED TO THE IRREGULAR SURFACE OF THE METAL ELEMENT, THE CONCRETE ELEMENT HAVING APERTURES WHICH WHEN THE CONCRETE ELEMENT IS IN PLACE ARE POSITIONED TO REGISTER WITH SAID NUTS, AND HEADED RODS OUTSTANDING IN THE SEVERAL APERTURES AND THREADEDLY RECEIVED IN THE CORRESPONDING NUTS, SAID RODS BEING INADEQUATE TO RESIST THE SHEAR LOADS, THE MORTAR FILLING EMBEDDING SAID RODS AND NUTS AND FILLING THE SEVERAL APERTURES, WHEREBY THE RODS ACT IN TENSION TO HOLD THE CONCRETE ELEMENT AGAINST SEPARATION FROM THE METAL ELEMENT, AND THE ROUGHENED SURFACES SO HELD TOGETHER RESIST SHEAR LOADS. 